Foodborne Pathogenic Strains Research Articles

Coconut husk waste products valorization for fabrication of luminescent titanium dioxide NPs as powerful tool for photodecomposition and food born infection: A sustainable strategy.

Fabricating metal oxide nanoparticles has garnered much attention lately because creating safe chemicals, sustainable materials, economic processes, and renewable resources is becoming increasingly important. This research shows how TiO2 nanoparticles (NPs) could be generated in an ecologically responsible way using waste coconut husk with the help of tender coconut. This extract functions as both a reducing agent and a sealing agent. The investigation of TiO2 NPs exploited ultraviolet (UV), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and field-emission scanning electron microscopy (FE-SEM) with energy-dispersive X-ray (EDX) methods. The germicidal properties of TiO2 NPs against food-borne pathogenic strains were studied using the agar well method. Employing Congo red pigment, the photodecomposition behavior was investigated. The TiO2 NPs produced had a crystallite size measuring 16.2nm. The average grain size of the sample, as measured by FE-SEM inspection, falls within the range of 15 to 25 nm. Impressive anti-germ effects against food-borne germs like Gram-positive (Staphylococcus aureus and Listeria monocytogenes), Gram-negative (Salmonella typhimurium and Escherichia coli) bacteria, and fungi (Candida albicans and Aspergillus niger) have been proved by the sustainable fabrication of TiO2 NPs. The catalytic effectiveness of Congo red decreased by 88% after 90 min. The findings suggest that sustainable synthesis of TiO2 NPs is an effective tool for food-borne germicides and photodecomposition behaviors.

Versatile Platinum Nanoparticles-Decorated Phage Nanozyme Integrating Recognition, Bacteriolysis, and Catalysis Capabilities for On-Site Detection of Foodborne Pathogenic Strains Vitality Based on Bioluminescence/Pressure Dual-Mode Bioassay.

Sensitive and on-site discrimination of live and dead foodborne pathogenic strains remains a significant challenge due to the lack of appropriate assay and signal probes. In this work, a versatile platinum nanoparticle-decorated phage nanozyme (P2@PtNPs) that integrated recognition, bacteriolysis, and catalysis was designed to establish the bioluminescence/pressure dual-mode bioassay for on-site determination of the vitality of foodborne pathogenic strains. Benefiting from the bacterial strain-level specificity of phage, the target Salmonella typhimurium (S.T) was specially captured to form sandwich complexes with P2@PtNPs on another phage-modified glass microbead (GM@P1). As the other part of the P2@PtNPs nanozyme, the introduced PtNPs could not only catalyze the decomposition of hydrogen peroxide to generate a significant oxygen pressure signal but also produce hydroxyl radicals around the target bacteria to enhance the bacteriolysis of phage and adenosine triphosphate release. It significantly improved the bioluminescence signal. The two signals corresponded to the total and live target bacteria counts, so the dead target could be easily calculated from the difference between the total and live target bacteria counts. Meanwhile, the vitality of S.T was realized according to the ratio of live and total S.T. Under optimal conditions, the application range of this proposed bioassay for bacterial vitality was 102-107 CFU/mL, with a limit of detections for total and live S.T of 30 CFU/mL and 40 CFU/mL, respectively. This work provides an innovative and versatile nanozyme signal probe for the on-site determination of bacterial vitality for food safety.

Antibacterial and Antibiofilm Activity of Eucalyptus camaldulensis Derived Fe3O4 Nano-particles against Foodborne Pathogens

Foodborne pathogens are zoonotic and multidrug resistant, which are not only affecting economy but also accountable for public health burdens. The present study was aimed to evaluate the efficacy of medicinal plant i.e., Eucalyptus camaldulensis extract mediated Fe3O4 and ZnO nanoparticles against the 27 foodborne pathogenic strains, isolated from milk, meat, dry fruits and vegetable samples collected from Multan, Pakistan. In phytochemical screening, the plant extract was found to contain numerous bioactive compounds including flavonoids, phenolic compounds, tannins, quinones, and anthocyanins. Fe3O4 NPs synthesized from Eucalyptus camaldulensis displayed the highest antibacterial activity with zones of inhibition of 12-13mm against pathogens. Fe3O4 NPs were found to have highest anti-inflammatory potential with recorded percentage of 67% at 40 μg/ml. Fe3O4 NPs also demonstrated the highest antibiofilm activity after 120 hours of incubation. For DDPH antioxidant assay, the highest antioxidant activity was displayed by Fe3O4 NPs and their absorbance recorded was 1.43. Therefore, Eucalyptus camaldulensis mediated Fe3O4 NPs proved as an effective and eco-friendly approach to combat multidrug resistance in bacterial infections throughcharacteristic antibacterial, antibiofilm and antioxidant properties.

Application of Slightly Acidic Electrolyzed Water as a Potential Sanitizer in the Food Industry

The food industry has extensively explored postharvest microbial control, seeking viable technologies to ensure food safety. Although numerous chlorine-based commercial sanitizers serve this purpose, many are plagued by constraints such as instability and diminished disinfectant efficacy. These issues arise from exposure to organic matter in wash water, light, or air. As an innovative and promising alternative, slightly acidic electrolyzed water (SAEW) has emerged, captivating attention for its robust sterilization potential and eco-friendliness in agricultural and food sectors. SAEW generated via electrolysis of a diluted hydrochloric acid (HCl) solution with concentrations ranging from 2 to 6% or aqueous solution of sodium chloride (NaCl) in a nonmembrane electrolytic chamber is reported to possess equivalent antimicrobial properties as strong acidic electrolyzed water (StAEW). In contrast to traditional chlorine sanitizers, SAEW leaves less chlorine residue on sanitized foods such fresh-cut fruit and vegetables, meat, poultry, and aquatic products due to its low available chlorine concentration (ACC). Its near neutral pH of 5 to 6.5 not only renders it environmentally benign but also mitigates the production of chlorine gas, a contrast to low pH conditions seen in StAEW generation. The bactericidal effect of SAEW against various strains of foodborne pathogens is widely believed and accepted to be due to the combined action of high oxidation-reduction-potential (ORP) reactions and undissociated hypochlorite/hypochlorous acid (HOCl). Consequently, a burgeoning interest surrounds the potential of SAEW for sanitation in the food industry, offering an alternative to address shortcomings in sodium hypochlorite solutions and even StAEW. It has been hypothesized from a number of studies that SAEW treatment can increase the quality and nutritional value of harvested fruits, which in turn may enhance their ability to be stored. Therefore, SAEW is not only a promising sanitizer in the food industry but also has the potential to be an efficient strategy for encouraging the accumulation of bioactive chemicals in plants, especially if it is used extensively. This review encapsulates the latest insights concerning SAEW, encompassing its antimicrobial effectiveness, sanitization mechanism, advantages vis-à-vis other sanitizers, and plausible applications across the food industry.

Biosynthesis and characterization of silver nanoparticles from Punica granatum (pomegranate) peel waste and its application to inhibit foodborne pathogens

Polyphenolics have been predicted to effectively develop antimicrobial agents for the food industry as food additives and promote human health. This study aims to synthesize pomegranate peel extract (PPE) with silver nanoparticles (AgNPs) against eight foodborne pathogens. Multispectroscopic analysis of UV–vis spectroscopy, Zeta potential, Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) analysis were used to characterize the interaction between PPE and AgNPs. Eight foodborne pathogenic strains (six bacterial and two fungal strains) Bacillus subtilis ATCC 6633, Enterococcus faecalis ATCC 29212, Escherichia coli ATCC 8379, Klebsiella pneumoniae ATCC 00607, Salmonella typhi DSM 17058, Shigella sonnei DSM 5570, Aspergillus flavus ATCC 9643, and Rhizopus oryzae ATCC 96382 were used to test the inhibitory potential of PPW-AgNPs. The reaction colour of PPE-AgNPs from yellow to brown indicated that the nanoparticles were successfully formed. The UV absorption of PPE-AgNPs was detected at 440 nm of 0.9 SPR. SEM image of PPE-AgNPs exhibited spherical shapes with a zeta potential of − 20.1 mV. PPE-AgNPs showed high antimicrobial activity against all tested strains. The highest inhibition activity of PPE-AgNPs was recorded for the B. subtilis strain followed by K. pneumonia, while the highest resistance was noticed for R. oryzae. The components of pomegranate peel were analyzed using gas chromatography–mass spectrometry (GC–MS). The major constituents of pomegranate peel is phenol (51.1%), followed by Isocitronellol (19.41%) and 1-Propanol, 2-(2-hydroxypropyl)- (16.05%). PPE is key in the simple, eco-friendly green synthesis of extracellular stable AgNPs as an alternative source for harmful chemical disinfectants.

Ultrasensitive and Specific Phage@DNAzyme Probe-Triggered Fluorescent Click Chemistry for On-Site Detection of Foodborne Pathogens Using a Smartphone.

Rapid, specific, and on-site detection of virulent foodborne pathogenic strains plays a key role in controlling food safety. In this work, an ultrasensitive and specific Phage@DNAzyme signal probe was designed to detect foodborne pathogens. The proposed sensing probe was composed of the selected phage and functionalized DNAzyme, which realized the specific recognition of target foodborne pathogens at the strain level and the efficient catalysis of copper(II) based azide-alkyne cycloaddition (CuAAC) click reaction with fluorescent signal, respectively. As a proof of concept, the virulent Escherichia coli O157:H7 (E. coli O157:H7) as the representative analyte was first enriched and purified from the complex food samples by a 4-mercaptophenylboronic acid-modified gold slide. Following, the Phage@DNAzyme probes were specifically combined with the captured E. coli O157: H7 and catalyzed the click reaction between 3-azido-7-hydroxycoumarin and 3-butyn-1-ol with the assistance of Cu(II) to generate a visual fluorescent signal. Finally, the corresponding fluorescent signals were measured by a smartphone to quantify the target concentrations. Under optimized conditions, the bioassay exhibited a wide linear range from 102 to 108 CFU/mL and the detection limit was 50 CFU/mL (S/N = 3). It was further extended to the detection of another foodborne pathogen Salmonella typhimurium with satisfying sensing performances. This work gives a new path for developing rapid, specific, and on-site detection methods for trace levels of pathogenic strains in foods.

Bioactive Compounds, Antioxidant, and Antibacterial Activity Against MDR and Food-Borne Pathogenic Bacteria of Psidium guajava. L Fruit During Ripening.

Psidium guajava fruits are highly appreciated for their nutrients and bioactive compounds content, which contribute to their antioxidant and antimicrobial capacities. The purpose of this study was to determine bioactive compound (phenolic, flavonoids, and carotenoid contents), antioxidant activity (DPPH, ABTS, ORAC, and FRAP), and antibacterial potential against MDR and food-borne pathogenic strains of Escherichia coli, and Staphylococcus aureus during different stages of fruit ripening.The results elucidated that ripe fruits (methanolic extract) contain the highest total phenolic, flavonoids, and carotenoid contents (417.36 ± 2.63µg GAE/gm of FW, 711.78 ± 0.70µg QE/gm of FW and 0.683 ± 0.06µg/gm of FW) followed by hexane, ethyl acetate, and aqueous. Methanolic extract of the ripe fruits showed the highest antioxidant activity when measured by DPPH (61.55 ± 0.91%), FRAP (31.83 ± 0.98mM Fe(II)/gm of FW), ORAC (17.19 ± 0.47mM TE/ gm of FW), and ABTS (41.31 ± 0.99µmol Trolox/gm of FW) assays. In the antibacterial assay, the ripe stage had the highest antibacterial activity against MDR and food-borne pathogenic strains of Escherichia coli, and Staphylococcus aureus. The methanolic ripe extract was found to possess maximum antibacterial activity ZOI, MIC, and IC50 18.00 ± 1.00mm, 95.95 ± 0.05%, and 0.58μg/ml; 15.66 ± 0.57mm, 94.66 ± 0.19%, and 0.50μg/ml, respectively, against pathogenic and MDR strains of E. coli and 22.33 ± 0.57mm, 98.97 ± 0.02%, and 0.26μg/ml; 20.33 ± 1.15mm, 96.82 ± 0.14%, and 0.39μg/ml, respectively, against pathogenic and MDR strains of S. aureus. Considering the bioactive compounds and beneficial effects, these fruitextracts could be promising antibiotic alternatives, avoiding antibiotic overuse and its negative effects on human health and the environment, and can be recommended as a novel functional food.

Biopreservative Effect of the Tunisian Halophyte Lobularia maritima Flavonoid Fraction, Used Alone and in Combination with Linalool in Stored Minced Beef Meat.

In the present study, Lobularia maritima (Lm) flavonoid extract (LmFV) was characterized by HPLC analyses and five compounds were detected. Further, to describe the chemical content of the matrix, GC-MS analyses after silylation were performed; the obtained results showed the presence of a large number of components belonging to several chemical classes, mostly sugar alcohols, sugars, fatty acids, and terpenes. Firstly, the antibacterial activities of this fraction and linalool (Lin) were evaluated against eight foodborne pathogenic strains with MIC values between 2.3 and 5.8 mg/mL and 0.23 and 0.7 mg/mL, respectively. Then, the antioxidant activity of both was evaluated by the DPPH antiradical test and the phosphomolybdenum test. Furthermore, the biopreservative effect of LmFV alone and in combination with Lin on minced beef stored at 4 °C for 14 days was evaluated using microbiological and physiochemical tests. LmFV at 4.6% alone significantly reduced microbial spoilage in ground meat (p < 0.05). The combination of LmFV (4.6%) and Lin (0.46%) was more effective than LmFV alone in inhibiting bacterial contamination, reducing TBARS values and the risk of bacterial contamination, and reducing the accumulation of Met myoglobin (MetMb). This combination, therefore, extends the shelf life of the product by about 10 days. Based on these microbiological results and physicochemical parameters, it can be stated that the addition of Lin potentiates the flavonoid fraction of L. maritima more strongly against the deterioration of meat quality by significantly improving its biopreservative effect as a natural conservative.

Detection of Methicillin-Resistant Staphylococcus aureus among Foodborne Pathogenic Strains and Assessment of Their Adhesion Ability and Cytotoxic Effects in HCT-116 Cells.

Staphylococcus aureus is one of the high-threat pathogens equipped with a repertoire of virulence factors making it responsible for many infections in humans, including foodborne diseases. The present study aims to characterize antibiotic resistance and virulence factors in foodborne S. aureus isolates, and to investigate their cytotoxic effects in human intestinal cells (HCT-116). Our results revealed methicillin resistance phenotypes (MRSA) along with the detection of mecA gene (20%) among tested foodborne S. aureus strains. Furthermore, 40% of tested isolates showed a strong ability for adhesion and biofilm formation. A high rate of exoenzymes production by tested bacteria was also registered. Additionally, treatment with S. aureus extracts leads to a significant decrease in HCT-116 cell viability, accompanied by a reduction in the mitochondrial membrane potential (MMP), as a result of reactive oxygen species (ROS) generation. Thereby, S. aureus food poisoning remains daunting and needs particular concern to prevent foodborne illness.

Metabolomic approaches for the detection of Listeria monocytogenes and Staphylococcus aureus in culture media

This study aimed to determine the changes in metabolites in the culture media of foodborne pathogens using nuclear magnetic resonance (NMR) spectroscopy. Extracellular metabolites in tryptic soy broth inoculated with none, Listeria monocytogenes ATCC 19111, and Staphylococcus aureus ATCC 29213 and 27213 at 37 °C were collected and analyzed by 1D 1H NMR and 2D 1H–13C heteronuclear single quantum coherence (HSQC) NMR. Partial least squares discriminant analysis revealed an excellent variable influence on projection (VIP) score and predictive ability among the different culture media metabolites. Based on presence/absence, five extracellular metabolites (cadaverine, histidine, nicotinate, putrescine, and succinate) were only detected in culture media containing pathogens. According to the pathogen species, L. monocytogenes and S. aureus ATCC 29213 could be distinguished based on changes in 11 metabolites (tyrosine, betaine, glycine, pyroglutamate, fumarate, alanine, putrescine, arginine, inosine, threonine, and sucrose). Moreover, different strains of S. aureus (ATCC 29213 and 27213) were distinguished using hypoxanthine and putrescine. Overall, extracellular metabolites in culture media could be used to detect the presence/absence, species, and even different strains of foodborne pathogens.

Highly sensitive multiplex detection of foodborne pathogens using a SERS immunosensor combined with novel covalent organic frameworks based biologic interference-free Raman tags

Rapid and reliable multiplex detection of foodborne pathogens is in great demand for ensuring food safety and preventing foodborne diseases. In this study, we developed a highly sensitive SERS immunosensor for the simultaneous detection of multiple foodborne pathogens. Novel biologic interference-free Raman tags synthesized by using the covalent organic frameworks (COF) TBDP as nanocontainer to load biologic interference-free Raman reporters and specific antibodies for interested targets were used to convert and amplify signals of foodborne pathogens. In addition, lectin functionalized magnetic nanoparticles (MNPs@Con A) which could efficiently bind to the carbohydrate constituents on the surface of pathogens were prepared to capture and isolate multiple pathogens simultaneously. The recognition of the target foodborne pathogen impels the generation of sandwich-like composites of MNPs@Con A/pathogen/TBDP@Raman tags, and these composites could be quickly separated from the sample matrix with the assistance of an external magnet. Besides, a mass of Raman reporters was released by eluting the collected MNPs@Con A/pathogen/TBDP@Raman tags composites. Combined with a portable Raman system, characteristic Raman signals (2271 and 2113 cm−1) of the occupied reporters located at the biologic interference-free region were observed and used for the simultaneous detection of two different foodborne pathogenic strains. And an equal limit of detection of 101 CFU/mL was achieved for each strain. This strategy provides new insight into the application of SERS in the detection of pathogenic bacteria.

Developing an affordable hyperspectral imaging system for rapid identification of Escherichia coli O157:H7 and Listeria monocytogenes in dairy products

The objective of this foundational study was to develop and evaluate the efficacy of an affordable hyperspectral imaging (HSI) system to identify single and mixed strains of foodborne pathogens in dairy products. This study was designed as a completely randomized design with three replications. Three strains each of Escherichia coli O157:H7 and Listeria monocytogenes were evaluated either as single or mixed strains with the HSI system in growth media and selected dairy products (whole milk, and cottage and cheddar cheeses). Test samples from freshly prepared single or mixed strains of pathogens in growth media or inoculated dairy products were streaked onto selective media (PALCAM and/or Sorbitol MacConkey agar) for isolation. An isolated colony was selected and mixed with 1 ml of HPLC grade water, vortexed for 1 min, and spread over a microscope slide. Images were captured at 2000× magnification on the built HSI system at wavelengths ranging from 400 nm to 1100 nm with 5‐nm band intervals. For each image, three cells were selected as regions of interest (ROIs) to obtain hyperspectral signatures of respective bacteria. Reference pathogen libraries were created using growth media, and then test pathogenic cells were classified by their hyperspectral signatures as either L. monocytogenes or E. coli O157:H7 using k‐nearest neighbor (kNN) and cross‐validation technique in R‐software. With the implementation of kNN (k = 3), overall classification accuracies of 58.97% and 61.53% were obtained for E. coli O157:H7 and L. monocytogenes, respectively.

In vitro bioactivity of the fractions and isolated compound from Combretum elaeagnoides leaf extract against selected foodborne pathogens

Ethnopharmacological relevanceCombretum species are used traditionally for the treatment of diarrhoea, hookworm, fever, inflammation, pain and infectious diseases. Infections are commonly caused by the intake of food contaminated with foodborne pathogens. These are a significant concern in the food industry owing to their ability to form biofilms and cause food spoilage, despite the availability of modern food preservation techniques. Combretum elaeagnoides Klotzsch (Combretaceae) is used in southern African traditional medicine against infections and diarrhoea. Aim of the studyThis study evaluated the antimicrobial ability of C. elaeagnoides leaf fractions and the isolated compound quercetin-3-O-rhamnoside against a panel of foodborne pathogens, and biofilms formed by them. The samples were also assessed for their antioxidant activity and cytotoxicity. Materials and methodsFractions prepared from the methanol extract of the leaves, and a bioactive compound (quercetin-3-O-rhamnoside) isolated from the ethyl acetate fraction were investigated for activity against nine reference and clinical strains of foodborne pathogens. The microdilution method was used to determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of the fractions and compound. The inhibition of biofilm formation and the crystal violet staining assays were used to determine the antibiofilm efficacy. The DPPH (2, 2-diphenyl-1-picrylhydrazyl) assay and the 2, 2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) electron reduction assay were used to determine the antioxidant potential of the fractions and compound. The cytotoxicity was assessed using the 3-(4, 5-dimethylthiazolyl-2)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric assay against Vero African monkey kidney cells. ResultsThe fractions were active against all tested organisms, with MIC values ranging from 0.03 to 1.25 mg/mL. The best MBC was 0.63 mg/mL. All the fractions and the purified compound inhibited biofilm formation of Staphylococcus aureus and Salmonella Typhimurium, with percentage inhibition values greater than 50% at 1 mg/mL. The compound had very promising antibiofilm activity against Escherichia coli 1 (ATCC 25922) with percentage inhibition of >150%. The compound and fractions had good radical scavenging potential against the DPPH and ABTS radicals. Quercetin-3-O-rhamnoside and the fractions were relatively non-cytotoxic. ConclusionThe ability of the fractions and compound to reduce and inhibit biofilm biomass and their promising antioxidant potential provide motivation to further investigate the use of plants to protect food products from contamination, as well as to treat infections characterized by bacterial biofilms.

Pastırmadaki Potansiyel Bakteriyosinojenik Laktik Asit Bakterileri

Recent researches conducted have focused on the possibility of using bacteriocin produced by lactic acid bacteria both (LAB) as protective cultures and as natural antimicrobial agents in dry cured meat products such as pastirma. In the present study, 50 lactic acid bacteria strains, previously isolated from various traditional pastirma samples, were tested for their antimicrobial potentials. Determination of antagonistic activities against food-borne pathogenic strains (Listeria monocytogenes, Staphylococcus aureus and Bacillus cereus) were done by using agar-spot and well diffusion assays. Then, active isolates were identified by using 16S rRNA gene sequence analysis. According to the results, 11 of tested LAB were determined with significant bacteriocinogenic potential and these were assigned to as 1 Lactobacillus plantarum, 9 L. plantarum subsp. plantarum and 1 Pediococcus pentosaceus. In conclusion, it was reached that the isolated/identified bacteriocin-producing lactic acid bacteria strains from pastirma samples have a significant potential to prepare pure or crude bacteriocin preparations.

Microalgae: A new source of healthy ingredients. Antioxidant and antimicrobial properties and incorporation as a functional ingredient for cheese making

AbstractAntimicrobial and antioxidant activities of nine species of microalgae have been determined to study its potential as healthy ingredients for functional foods. In order to determine the antioxidant capacity, two different techniques have been used. Firstly, a colorimetric test was carried out in order to detect the presence of lipophilic and hydrophilic antioxidant compounds, this method is based on the detection of the radical ABTS + , which is produced by the oxidation of ABTS in the presence of potassium persulfate, detection of the radical ABTS + decreases in the presence of antioxidant compounds. Also the ORAC test was also applied for this purpose. Results with both methods showed very promising results for Rhodomonas lens. Thus this species was chosen to develop a functional cheese and study the healthy properties that the microalgae confer on it.To determine the antimicrobial activity five food food-borne pathogenic strains were used: Escherichia coli CECT 516, Enterococcus faecalis CECT 481, Listeria monocytogenes CECT 935, Salmonella enterica CECT 4594 and S. aureus CECT 435. First, extracts of different polarity were obtained from microalgae. From each species, 4 extracts were obtained using different solvents of higher to less polarity (MilliQ Water, ethanol, ethyl acetate and hexane). The use of these solvents is common in the preparation of plant extracts, since they ensure the solubility of most of the compounds of interest and do not show toxicity after evaporation to determine the antimicrobial activity. The agar diffusion technique was used and the plates were kept refrigerated at 4 ° C for 1 h to allow the extracts to diffuse through the agar and subsequently incubated at 37 ° C for 24 h to allow microbial growth. After that time the presence of inhibition halos was observed around the perforations of the plates. Results showed that the ethanolic extract presented more antimicrobial activity than the extracts using MilliQ Water, ethyl acetate or hexane. Salmonella was not inhibited by any of the extracts studied.

Lanthanide-labeled fluorescent-nanoparticle immunochromatographic strips enable rapid and quantitative detection of Escherichia coli O157:H7 in food samples

A simple, rapid, highly sensitive, and quantitative fluorescence-based immunochromatographic test (ICT) was successfully developed for the determination of Escherichia coli O157:H7 in food samples. Europium (III) chelated nanoparticles (EuNPs) conjugated to monoclonal antibodies specific to the O-specific polysaccharide fractions of E. coli O157:H7 were used as the fluorescence reporter. The fluorescence was visually observable within 15 min under dark conditions with an ultraviolet light source, and a test-strip reader was used for quantitative analysis. Under optimal conditions, the visual limit of detection (LOD) of the strip was 104 CFU/mL, and the LOD for quantitative detection was as low as 5 × 102 CFU/mL with the test-strip reader. No cross-reaction was observed in six E. coli strains with different somatic (O) antigens and five other major foodborne pathogenic strains, thus indicating the good specificity of this method. Additionally, the detection sensitivity of E. coli O157:H7 was improved to 1 CFU/mL of the original bacterial content by pre-incubation for 8 h in meat (beef, pork, and chicken) and 6 h in milk samples. The average recovery of E. coli O157:H7 spiked in pork was 84.5–103%, thus indicating the accuracy and reliability of the novel test strips. The developed EuNP-ICT strip assay is highly sensitive, specific, and replicable. This detection system provides a tool that can potentially be used to detect E. coli O157:H7 and other pathogenic bacteria in food samples.

Enzymatic Inactivation of Pathogenic and Nonpathogenic Bacteria in Biofilms in Combination with Chlorine

This study investigated the effects of enzyme application on biofilms of bacterial isolates from a cafeteria kitchen and foodborne pathogens and the susceptibility of Salmonella biofilms to proteinase K combined with chlorine treatment. For four isolates from a cafeteria kitchen ( Acinetobacter, Enterobacter, and Kocuria) and six strains of foodborne pathogens ( Salmonella enterica, Staphylococcus aureus, and Vibrio parahaemolyticus), the inhibitory effect of enzymes on biofilm formation at 25°C for 24 h or the degradative efficacy of enzymes on 24-h mature biofilm at 37°C for 1 h in tryptic soy broth (TSB) was examined in a polystyrene microtiter plate. The effect of enzymes was also evaluated on a subset of these strains in 20 times diluted TSB (1/20 TSB) at 25°C. The working concentrations of five enzymes were 1 U/100 μL for α-amylase, amyloglucosidase, cellulase, and DNase and 1 milli-Anson unit/100 μL for proteinase K. In addition, 24-h mature Salmonella Typhimurium biofilm on a stainless steel coupon was treated with proteinase K for 1 h at 25°C followed by 20 ppm of chlorine for 1 min at 25°C. The results showed that certain enzymes inhibited biofilm formation by the kitchen-originated bacteria; however, the enzymatic effect was diminished on the mature biofilms. Biofilm formation of V. parahaemolyticus was suppressed by all tested enzymes, whereas the mature biofilm was degraded by α-amylase, DNase I, and proteinase K. Proteinase K was effective in controlling Salmonella biofilms, whereas a strain-dependent variation was observed in S. aureus biofilms. In 1/20 TSB, Enterobacter cancerogenus and Kocuria varians were more susceptible to certain enzymes during biofilm formation than those in TSB, whereas the enzymatic effect was much decreased on 24-h mature biofilms, regardless of nutrient conditions. Furthermore, synergistic inactivation of Salmonella Typhimurium in biofilms was observed in the combined treatment of proteinase K followed by chlorine. Live/Dead assays also revealed a decrease in density and loss of membrane integrity in Salmonella Typhimurium biofilms exposed to the combined treatment. Therefore, certain enzymes can control biofilms of isolates residing in a cafeteria kitchen and foodborne pathogens. This study demonstrates the potential of enzymes for the sanitation of food processing environments and of proteinase K combined with chlorine to control Salmonella biofilms on food contact surfaces.

Biomimetic surface modifications of stainless steel targeting dairy fouling mitigation and bacterial adhesion

This work aims at presenting and comparing the antifouling and antibacterial behaviour of three biomimetic surfaces targeting dairy fouling reduction, namely atmospheric plasma-sprayed silane-based thin films, lubricated slippery surfaces and femtosecond laser textured lotus-like surfaces. Fouling tests were conducted on a pilot-scale pasteurization plant fed with a model whey protein and calcium foulant solution and tested samples were placed in isothermal holding-like conditions. Detailed characterizations of the substrates before and after fouling test allowed connecting their surface properties to their antifouling performances. The best result was obtained with the nano-rough plasma coatings which led to a substantial fouling reduction for two consecutive pasteurisation runs. These surfaces were subsequently tested towards bacterial adhesion with three different foodborne pathogenic strains, again demonstrating better performances than bare stainless steel.

Development and evaluation of an up-converting phosphor technology-based lateral flow assay for rapid detection of Francisella tularensis.

Francisella tularensis is a potential biowarfare/bioterrorism agent and zoonotic pathogen that causes tularemia; thus, surveillance of F. tularensis and first-level emergency response using point-of-care testing (POCT) are essential. The UPT-LF POCT assay was established to quantitatively detect F. tularensis within 15 min, and the sensitivity of the assay was 104 CFU · mL−1 (100 CFU/test). The linear quantitative range covered five orders of magnitude, and the coefficients of variation were less than 10%. Except Shigella dysenteriae, UPT-LF showed excellent specificity to four strains that are also potential biowarfare/bioterrorism agents and 13 food-borne pathogenic strains. Samples with pH 2–13, high ion strengths (≥2 mol · L−1 solution of KCl and NaCl), high viscosities (≤50 mg · mL−1 PEG20000 or ≥20% glycerol), and high concentrations of biomacromolecules (≥400 mg · mL−1 bovine serum albumin or ≥80 mg · mL−1 casein) showed little influence on the assay. For practical utilization, the tolerance limits for seven powders and eight viscera were determined, and operation errors of liquid measurement demonstrated a minor influence on the strip. Ftu-UPT-LF is a candidate POCT method because of its excellent sensitivity, specificity, and stability in complex samples, as well as low operation error.

Broad and efficient control of major foodborne pathogenic strains of Escherichia coli by mixtures of plant-produced colicins

Enterohemorrhagic Escherichia coli (EHEC) is one of the leading causes of bacterial enteric infections worldwide, causing ∼100,000 illnesses, 3,000 hospitalizations, and 90 deaths annually in the United States alone. These illnesses have been linked to consumption of contaminated animal products and vegetables. Currently, other than thermal inactivation, there are no effective methods to eliminate pathogenic bacteria in food. Colicins are nonantibiotic antimicrobial proteins, produced by E. coli strains that kill or inhibit the growth of other E. coli strains. Several colicins are highly effective against key EHEC strains. Here we demonstrate very high levels of colicin expression (up to 3 g/kg of fresh biomass) in tobacco and edible plants (spinach and leafy beets) at costs that will allow commercialization. Among the colicins examined, plant-expressed colicin M had the broadest antimicrobial activity against EHEC and complemented the potency of other colicins. A mixture of colicin M and colicin E7 showed very high activity against all major EHEC strains, as defined by the US Department of Agriculture/Food and Drug Administration. Treatments with low (less than 10 mg colicins per L) concentrations reduced the pathogenic bacterial load in broth culture by 2 to over 6 logs depending on the strain. In experiments using meats spiked with E. coli O157:H7, colicins efficiently reduced the population of the pathogen by at least 2 logs. Plant-produced colicins could be effectively used for the broad control of pathogenic E. coli in both plant- and animal-based food products and, in the United States, colicins could be approved using the generally recognized as safe (GRAS) regulatory approval pathway.